The present invention relates to an audio/video synchronous reproducer and a method of audio/video synchronous reproduction which carry out audio reproduction and video display synchronously based on audio data and video data. Techniques of this kind are described in, for example, JP-A-06-343065 and JP-A-09-149411.
In such an audio/video synchronous reproducer, audio data and video data digitally stored in a storage medium, such as DVD-ROM, a CD-ROM and a hard disk, are read out therefrom so as to carry out audio reproduction and video reproduction based on those data via a loudspeaker and a CRT monitor, respectively. The audio/video synchronous reproducer is proposed in Japanese Patent Application No. 09-001922 which is laying-opened as JP-A-10-200862 after the Convention date of the instant patent application. This audio/video synchronous reproducer will be explained as an earlier art in more detail with reference to FIG. 8.
Referring to FIG. 8, the audio/video synchronous reproducer comprises a data storage 101 storing compressed and multiplexed digital audio and video data, an AV separating section 102 for reading out the data from the data storage 101 and separating them into audio data and video data, a video processing section 103 for decompressing or expanding the video data separated at the AV separating section 102, an audio processing section 104 for expanding the audio data separated at the AV separating section 102, an AV synchronous control section 105 for performing an audio/video synchronous control, a CRT monitor 106 for performing video display based on the expanded video data, and a loudspeaker 107 for performing audio reproduction based on the expanded audio data.
However, the audio/video synchronous reproducer shown in FIG. 8 does not consider the case wherein audio data and video data have their own reference times which are independent and different from each other.
Further, if there exists mismatching between time stamps included in video data and the number of video frames, the expected reproduction result can not be achieved. The reason for this is that time stamps included in audio data or video data are not used.
Further, there rises a case wherein the accuracy of a reference time to be used for audio/video synchronization is not sufficient. The reason for this is that a processed audio data amount if used as a reference time as it is. If the reference time accuracy is not sufficient, there rises a case wherein the accuracy of the processed audio data amount is lowered. As a result, the accuracy of the audio/video synchronization is also lowered.
It is therefore an object of the present invention to provide an improved audio/video synchronous reproducer that can eliminate one or more of the disadvantages inherent in the foregoing conventional technique.
It is another object of the present invention to provide an improved method of audio/video synchronous reproduction that can eliminate one or more of the disadvantages inherent in the foregoing conventional technique.
Other object of the present invention will become clear as the description proceeds.
According to one aspect of the present invention, there is provided an audio/video synchronous reproducer for carrying out audio reproduction and video display synchronously in response to audio data and video data. The audio/video synchronous reproducer comprises video processing means for processing the video data to produce a video display control signal and a video time stamp, video display means connected to the video processing means for performing the video display in accordance with the video display control signal, audio processing means for processing the audio data to produce an audio reproduction control signal and a processed audio data amount, audio reproducing means connected to the audio processing means for performing the audio reproduction in accordance with the audio reproduction control signal, video time stamp detecting means connected to the video processing means for detecting the video time stamp, audio time stamp deriving means connected to the audio processing means for deriving an audio time stamp equivalent value based on the processed audio data amount, time stamp comparing means connected to the video time stamp detecting means and the audio time stamp deriving means for comparing the video time stamp with the audio time stamp equivalent value to produce a comparison result signal indicative of a delayed/advanced relationship between the video data and the audio data, and video control means connected to the video processing means and the timestamp comparing means for controlling an operation of the video processing means in response to the comparison result signal.
According to another aspect of the present invention, there is provided an audio/video synchronous reproducer comprising an AV synchronous control section for performing comparison between a video time stamp assigned to video data and an audio time stamp equivalent value derived based on a processed amount of audio data, the AV synchronous control section controlling video display according to a result of the comparison so as to be synchronous with audio reproduction.
According to still another aspect of the present invention, there is provided a method of audio/video synchronous reproduction comprising the steps of detecting a video time stamp assigned to video data; deriving an audio time stamp equivalent value based on a processed amount of audio data; performing comparison between the video time stamp and the audio time stamp equivalent value; and controlling video display according to a result of the comparison so as to be synchronous with audio reproduction.